Production of charmed mesons inZ decays

Abstract

The production of charmed mesons$\mathop {D^0 }\limits^{( - )}$,D ^±, andD ^*± is studied in a sample of 478,000 hadronicZ decays. The production rates are measured to be

$$\begin{gathered} \frac{{\Gamma ({\rm Z} \to D^{* \pm } X)}}{{\Gamma _{had} }} = 0.187 \pm 0.015(\exp .) \pm 0.013(BR), \hfill \\ \frac{{\Gamma ({\rm Z} \to D^ \pm X)}}{{\Gamma _{had} }} = 0.251 \pm 0.026(\exp .) \pm 0.025(BR), \hfill \\ \frac{{\Gamma ({\rm Z} \to \mathop {D^0 }\limits^{( - )} X)}}{{\Gamma _{had} }} = 0.518 \pm 0.052(\exp .) \pm 0.035(BR), \hfill \\ \end{gathered} $$

where the errors from this analysis are separated from those coming from theD branching ratios (BR). TheD ^*± momentum distribution is extracted separately for$Z \to c\bar c$ and$Z \to b\bar b$ events with the help of event shape variables. It is consistent with the prediction of the JETSET Monte Carlo program after adjustment of the charm fragmentation function. Constraining the shape of the$Z \to b\bar b$ contribution, the average fraction of the beam energy taken by aD ^* meson produced in the fragmentation of a charm quark is extracted by a parametric fit to be <X _E > _c =0.495±0.011±0.007. Evidence forD ^**0 (D ₁(2420)⁰ and/orD ^*₂ (2460)⁰) production is found in the$D^{* \pm } \pi ^ \mp$ channel, accounting for a fraction (18±5±2)% of allD ^*± production. The relative production of vector and pseudoscalar mesons is dicussed, together with the possible effects ofD ^** production. Thec-quark forward-backwardZ-pole asymmetry is detrmined from that of high momentumD ^*± to beA ^0,c _FB =(7.7±4.4)%.